Question

multiply and add like terms: (z + 3)(z - 3)

Explanation:

Step1: Use FOIL method

$(z + 3)(z - 3)=z\times z+z\times(-3)+3\times z + 3\times(-3)$

Step2: Simplify each term

$z\times z=z^{2}$, $z\times(-3)=-3z$, $3\times z = 3z$, $3\times(-3)=-9$
So we have $z^{2}-3z + 3z-9$

Step3: Combine like - terms

$-3z+3z = 0$, so the result is $z^{2}-9$

Answer:

$z^{2}-9$